Related Party Transactions and Arrangements (Indirect Affiliate Expenses) (Detail) (Affiliated Entity [Member], USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Related Party Transaction [Line Items]
Related Party Transaction, Expenses from Transactions with Related Party	$ 65,452	$ 20,032	$ 332,923	$ 348,086
Audrain Building [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Expenses from Transactions with Related Party	4,769		8,691
ANST Office Build Out [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Expenses from Transactions with Related Party	114		449
New York Office [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Expenses from Transactions with Related Party	677		864
Dresher, PA Office [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Expenses from Transactions with Related Party	24		60
North Carolina Office [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Expenses from Transactions with Related Party	11		26
Indirect Affiliate Expenses [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Expenses from Transactions with Related Party	$ 5,595	$ 0	$ 10,090	$ 0